WASHINGTON - Livestock producers and big-food companies fighting in federal court over new meat labels are turning to Congress for help just as a trade dispute with neighboring Canada and Mexico over the labels is heating up.

The dispute pits businesses and foreign governments who fear Americans will discriminate against imported meat against groups that say consumers have a right to know where their food is coming from.

A coalition of trade associations and companies sent a letter to Congress this week saying that, if country-of-origin labels for meat are determined by the World Trade Organization to violate international trade rules, then lawmakers should order the U.S. Department of Agriculture to indefinitely suspend the meat labeling rule.

“The rule will cause consumer confusion, raise food prices, be costly to implement and serve no public health or food safety benefit,” Hormel Foods Corp. spokesman Rick Williamson said in an e-mail. Hormel joined two other Minnesota food companies, Cargill Inc. and General Mills Inc., in signing the letter.

Earlier this year, the meat industry argued unsuccessfully to a D.C. federal appeals court that the labeling rule violates companies’ constitutional free-speech rights. The full D.C. Court of Appeals agreed to rehear the case, where it is still under consideration.

Meanwhile, the WTO is investigating unfair trade practice charges filed against the U.S. by Mexico and Canada over the requirement that muscle cuts of meat packaged in the U.S. list the countries of origin. International trade rules are designed to prevent countries from imposing rules and costs that become barriers to trade. Even as the neighboring countries seek protection under those trade rules, they have expressed concern that Americans will stop buying meat that they know comes from other countries.

A WTO judgment that the meat labels violate trade rules could lead Mexico and Canada to slap retaliatory tariffs on food they get from the U.S.

“A finding of noncompliance would surely result in serious economic harm to U.S. firms that export to our neighbors,” the anti-labeling coalition wrote to agriculture leaders in Congress, including Rep. Collin Peterson of Minnesota, the ranking Democrat on the House committee.

“Canada has already issued a preliminary retaliation list targeting a broad spectrum of commodities and manufactured products that will affect every state in the country,” the letter continued. “Mexico has not yet announced a preliminary retaliation list.”

The WTO judged an earlier country-of-labeling proposal by the U.S. to violate its rules. The world trade group said labeling laws were allowed but not in the way the U.S. had applied them. The Agriculture Department changed its language in an attempt to answer WTO concerns.

Consumer groups steadfastly maintain that Americans want to know where their food comes from and have a legal right to know.

The meat industry and its allies “have hated country-of-origin labeling since it came up in 2002,” said Patty Lovera, assistant director of the consumer group Food and Water Watch. “They have thrown everything they could at it.”

Lovera said she and other advocates will examine the WTO decision, which is expected soon. But regardless of the decision, Lovera thinks the government should not back down from its labeling requirements. “If you ask the public, they want this label,” she said.

Aiming to jolt the rest of the world to action, President Barack Obama moved ahead Sunday with even tougher greenhouse gas cuts on American power plants, setting up a certain confrontation in the courts with energy producers and Republican-led states.